Nano-micelles Of Amphiphilic Polysaccharide Derivatives For Encapsulation Of Photosensitizers

Polysaccharides, such as chitosan and sodium alginate, widely exist in nature, which are non-toxic, biocompatible and biodegradable. Amphiphilic polysaccharide derivatives, consisting of the amphilic polysaccharide main chains and the hydrophobic segments, are promising to be used as drug delivery carriers. In photodynamic therapy (PDT), cells of tumor are killed by the reactive singlet oxygen produced from photosensitizers react with oxygen. Thus PDT is a promising method for the tumor therapy. The drug delivery systems of amphiphilic polysaccharide derivatives (APDs) and photosentitizers for tumor therapy were investigated in this work, mainly including the following parts:(1) Two kinds of APDs with different charges were synthesized, including: (a) amphiphilic deoxycholic acid groups grafted chitosan derivatives (Chit-DC), of which the polysaccharide main chain contains amino groups; (b) amphiphilic cholesteryl groups grafted sodium alginate derivatives (Alg-Chol), of which the polysaccharide main chain contains carboxylic groups. Their chemical structures were characterized by FTIR and 1H NMR spectroscopy. The pyrene fluorescence spectroscopy confirmed that the ADPs formed micelles in aqueous solution, and their critical aggregation concentration were determined to be 0.22 and 0.19 mg/mL, respectively.(2) The photosensitizers investigated in this work were 5,10,15,20-tetrakis(4-aminophenyl)-21H,23H-porphine (TAPP) and photofrin that is an oligo- porphine containing carboxylic groups, respectively. Four kinds of photosensitizer-loaded APDs micelles were prepared by self-assembly in phosphate buffer solution (PBS, pH 6.2), which were named as Chit-DC-Photofrin, Chit-DC-TAPP, Alg-Chol-Photofrin and Alg-Chol-TAPP. The result of UV-vis analysis showed that the photosensitizers were dispersed in the micelles. The dynamic diameters of the photosensitizer-loaded micelles were determined to be about 400-500 and 100-200 nm by dynamic light scattering analysis. The Chit-DC-Photofrin and Alg-Chol-TAPP micelles exhibited as the spheres observed in TEM images, and their size were about 300 and 100-200 nm. The result of Zeta potential analysis indicated that the surface ionic properties of the photosensitizer-loaded micelles were strongly influenced by the ionic photosensitizers.(3) The photodynamic properties of the photosensitizer-loaded APDs micelles were investigated by the steady fluorescence spectroscopy. The results indicated that the fluorescence quantum yields of the photosensitizers were obviously increased after being encapsulated by the APDs micelles. The fluorescence quenching concentrations of Photofrin in PBS (pH=6.2) and TAPP in THF were determined to be 2×10-5 and 8×10-6 g/mL, respectively.(4) The Alg-Chol-Photofrin exihibited killing effects on pancreatic cancer cell line (Panc-l), of which the mechanism was related to the inducement of cell death.